Since 1983
Oystercatchers have been systematically studied as part of a
long-term study of the University of Groningen, consequently many
Oystercatchers on the Dutch Wadden Sea island of Schiermonnikoog are
individually identifiable by their colour-rings. In total over 2500
individuals have been colour-banded, comprising adult breeders,
juvenile and adult non-breeders, as well as fledged young. Of these
banded individuals about 1000 are probably still alive right now,
of which most live on the island of Schiermonnikoog. Nonetheless,
Oystercatchers colour-banded on Schiermonnikoog have been reported
from all over the Netherlands, Belgium, Germany, Denmark, France, UK
and Norway.

Reports of
colour-ringed Oystercatchers (dead or alive) are very welcome as
they are crucial to understand survival and movement patterns of
Oystercatchers, which form the basis for understanding changes in
population numbers. Reports are preferentially send to us using a
standard form (click icon to download form).
We try to send each person that reports a bird to us a life-history
of that individual. An exact description of the colour-rings we use
is given below.

We use two different systems
of colour-rings, one with bands (left) and one with letters (right):

Description of the colour-ring systems used on Schiermonnikoog: colour-rings
with bars (left)

Each Oystercatcher has
three different rings at three different positions (see photo):
1. A metal ring from the Dutch Ringing Centre with a unique number on
it.
2. A large two-coloured barcode ring with horizontal bars of varying
width.
3. A small coloured ring without bars.

To determine the exact
identity of the individual we need to know 4 things: 1.The two colours of the barcode ring
We use 6 different combinations of barcode-rings, Marine rings
with White bars (MW), Green rings with White bars
(GW), White rings with Red bars (WR), Orange
rings with Black bars (OB), Red rings with Black
bars (RB) and Green rings with Black bars (GB).

2. The position and width
of the bars on the code ring.
Bars can be at three different positions, top, middle, or bottom. Bars
at the either three positions can be either absent (0), a thin bar (1)
or a thick bar (2). The barcode is read from top to below, yielding 19
different combinations:

3. The colour of the small coloured
ring without bars.
Small coloured rings are either of one or two colours. Unicoloured
rings are White (W), Red (R), Green (G), Black
(B) and Yellow (Y). Two-coloured rings are read from top to
bottom and can be Red-White (RW), Black-Green
(BG), White-Black (WB), White-Yellow (WY),
Green-Yellow (GY) and White-Red (WR).

4. The position of both the
barcode-ring and the small colored ring.
A birds leg consists of a tarsus (the part below the joint that looks
like a knee) and a tibia (the part above the joint that looks like
knee. The code ring is always on the tarsus, the small colored ring
can be either on the tarsus or tibia. The metal ring is always on the
tibia, but is not of any importance. There are six different
possibilities with the same barcode and color ring, named 1-6:

If we know combine step 1-4, we can identify the individual on the
photograph below:

1. The barcode-ring is White with
Red bars: WR
2. There is thin horizontal bar on the top of the barcode ring and no
bars in the middle or bottom part of the barcode-ring: 100
3. The small color-ring is Green: G
4. The small colour-ring is at the right tarsus and the barcode-ring
is at the left tarsus: 4.
(note that we take the perspective of the bird to determine left and
right)

The unique identity of this individual is
therefore: WR100G4

Description of the colour-ring systems used on Schiermonnikoog: colour-rings
with characters

Each Oystercatcher has four different rings at
four different positions (see drawing below and picture):
1. A metal ring from the Dutch Ringing Centre with a unique number on it.

2. Two large two-coloured rings with an
engraved characters which is repeated three times on the ring.

3. A small single-coloured ring

Of importance are

the exact position of each ring (left or
right, tibia or tarsus)

the exact colours (also of the engraved
character)

the exact character of each ring

The rings that are used:

The metal ring is always on the tibia (the
part above the joint that looks like a knee).

The small single-coloured rings can be White,
Yellow, Red, Green, Orange and Black

The character rings can be White, Yellow and
Orange with a black engraved character or Red and Green with a white
engraved character. The characters used are A, B, C, E, H, J, K, L, N, P,
Q, S, T, Y, Z. Character rings are always on the tarsus (the part below
the joint that looks like a knee).